1. Field of the Invention
The present invention relates to a precision balance which includes a weighing dish supported by a support member. The support member is guided by means of guide arms in such a way that the weighing dish performs essentially only a vertical movement during weighing. The precision balance further includes an adjusting device for adjusting the vertical spacing between the ends of two guide arms.
2. Description of the Prior Art
It is known to those skilled in the art that in balances of this type it is very important to maintain the exact parallel alignment of the guide arms. It is particularly important to maintain the exact vertical spacing between the guide arm ends, so that weighing errors are avoided which could occur when the material to be weighed is not placed in the center of the weighing dish.
Swiss Pat. No. 524,869 discloses a precision balance with an adjusting device in which the vertically extending structure of the balance is recessed underneath the surfaces for fastening the guide arm ends, so that these surfaces can be moved to a slight extent by bending the structure by means of a screw.
The known balance permits a fine adjustment to a limited extent of the vertical spacing between the ends of the guide arms arranged one above the other. However, bending of the structure causes stresses within the balance and a change in the horizontal spacing between the two ends of the guide arms, which leads to transverse forces in the guide arms and in the recess portions. These transverse forces are undesirable because they may lead to additional measurement errors.
It is, therefore, the primary object of the present invention to provide a precision balance in which the adjustment of the spacing between the guide arms can be carried out within the entire adjustment range by means of a single adjustment element, wherein the surfaces for fastening the ends of the guide arms are shifted parallel to one another within the entire adjustment range.
It is another object of the invention to make it possible to effect from the outside under operating conditions, i.e., without removing any housing parts, an adjustment of the spacing for compensating for errors caused by loads placed on the corners of the weighing dish.